Why +2lbs On The Cross?

**HORACE** · 02-14-2005, 07:14 AM

Hi.
Very interesting all that. I play tennis, and have a stringing machine ( Tyger Profi 55 ) and although we are talking about different tensions and guages, the principles remain the same ...
I have been bothered for some time about the fact that the crosses are obviously less tight than the mains because of the reasons already mentioned, i.e. that the crosses tighten the mains as they ( the crosses )are pulled. An effect of this must surely be that the ball/shuttlecock is send back mainly under power from the resilience of the main strings only. The crosses must have little to do with it as the mains reach their maximum stretch point well before the crosses will even be tight !
This seems like a pretty undesirable situation. Surely if the mains and crosses had the same tension, better ball control would be the result - although, as the crosses are shorter, their maximum stretch point would be reached before that of the mains, so pêrhaps a slightly lower tension is after all desirable for the crosses !
But how can this be achieved ?... The tighter you pull the crosses, the more tension will be put on the mains, so a much lower tension seems desirable for the mains, and higher for the crosses... But, I've tried this, and it doesn't seem to work, as, the high tension on the crosses just pulls the mains even tighter !
For information, when I string my racket normally, the mains measure at 25Kilos, but the crosses at at only 12. This is lamentable ...
The only way I can see to keep tension even would be, starting at the middle of the racket, to string one main followed by one cross, one main, one cross, etc. etc... That way a main will tighten the cross, then a cross will tighten the main etc...
Trouble is, you will need around 4 clamps to acheive this. It is not possible with just 2 fixed clamps, and resorting to flying clamps results in less accuracy ....!
Another big problem, is that in normal stringing, each cross string has progressively more friction on it from the mains, resulting in less tension on the final crosses. Most people worry about even tension on both sides of the mains, but look at the way a ball is hit, and you will see that the racket is more in a horizontal position than a vertical one ( in tennis anyway ), so the balance of the crosses on either end is actually more important...
I remember I once saw on the Fischer website, a factory worker stringing a racket, and he was using a device which held apart the mains, while he strung the crosses. The crosses did not touch the mains, and therefore avoided any friction. But where does one obtain such a device ?....
One final point. When I have my rackets strung on the big, expensive Babolat machines, they play better than mine ! However, they are strung conventially, with less care and attention than I give. I can only assume that the clamping system is of very high tolerence, with little freeplay, therefore minimizing tension loss. This is perhaps after all, the most important factor of all ... If only I could afford one .... !!

**catbear** · 03-09-2005, 12:43 AM

Hi All,

I just noticed that Yonex recommends 2 pounds higher tension for cross for their old models such as Ti10. But for the latest models, they only recommend 1 tension for both main and cross. Can anyone come up an explanation for it?

http://www.yonex.co.jp/badminton/old...ket/ti10r.html
http://www.yonex.co.jp/badminton/old...cket/mp80.html
http://www.yonex.co.jp/badminton/old...t/cab20lo.html
http://www.yonex.co.jp/badminton/pro...et/ns7000.html
http://www.yonex.co.jp/badminton/pro...ket/at800.html
http://www.yonex.co.jp/badminton/pro...cket/mp90.html

縦 means main. 横 means cross

Regards,
CB

**taneepak** · 03-09-2005, 03:08 AM

That is not how I read it. The 1lb difference is between a 2U and a 3U, or a 3U and a 4U. Even when Yonex is more specific, like when suggesting both main and cross tension, the 2lbs difference is a rough guide. A more accurate difference is 10%.

**LazyBuddy** · 03-09-2005, 10:03 AM

Originally Posted by taneepak

That is not how I read it. The 1lb difference is between a 2U and a 3U, or a 3U and a 4U. Even when Yonex is more specific, like when suggesting both main and cross tension, the 2lbs difference is a rough guide. A more accurate difference is 10%.

I agree.

The "1 lb" difference is referring to the "min and max" recommend tension between different models with different "U".

The "2 lb" difference that we are talking about, is the "main vs cross" for the same racket.

**catbear** · 03-09-2005, 06:05 PM

Hi Taneepak and LazyBuddy,

You guys misunderstood me. There is a 1 pound difference between 3U and 4U rackets. But for old models, they also recommend two tensions for main and cross:

For Ti 10:

3U縦17〜20、横19〜22
2U縦18〜21、横20〜23

For NS7000:
3U：19〜24
2U：20〜25

So for the older models, they recommended different tensions for main and cross, but this is no longer the case for the latest models...

Regards,
CB

Originally Posted by LazyBuddy

I agree.

The "1 lb" difference is referring to the "min and max" recommend tension between different models with different "U".

The "2 lb" difference that we are talking about, is the "main vs cross" for the same racket.

**taneepak** · 03-09-2005, 07:55 PM

There is no inconsistency. One is a brief classification of tension range, usually used in circumstances where space is limited, like on the cone of a racquet. The more detail tension range is usually indicated in Yonex's spec chart. For example, on my MP99 2U the small label on the cone of my racquet says 18-22lbs, 8-10kg, but the spec chart says Main 18-20lbs 8-9kg, Cross 20-22lbs 9-10kg.
Despite its modest tension range of 18-22lbs, I string my MP99 to 27-29.5lbs.

**Neil Nicholls** · 03-10-2005, 02:35 AM

Originally Posted by catbear

For NS7000:
3U：19〜24
2U：20〜25

So for the older models, they recommended different tensions for main and cross, but this is no longer the case for the latest models...

It might depend on your source.
I have the UK Yonex badminton catalog 2005 and it says

NS7000 3U Main 19-22 lbs Cross 21-24 lbs
NS8000 3U Main 19-22 lbs Cross 21-24 lbs
AT800OF 4U Main 19-22 lbs Cross 21-24 lbs
AT800DE 4U Main 19-22 lbs Cross 21-24 lbs
AT500 3U Main 20-23 lbs Cross 22-25 lbs
AT300 3U Main 20-23 lbs Cross 22-25 lbs
MP99 3U Main 17-20 lbs Cross 19-22 lbs
MP88 4U Main 16-19 lbs Cross 18-21 lbs

**SWC_Ant** · 03-31-2005, 12:39 AM

Originally Posted by Neil Nicholls

From measurements on a strung racquet, I calculate that the mains are stretched by about 0.027mm per cross string. This is for 0.7mm diameter string.

With 23 crosses this adds about 0.6mm to the mains.
Centre mains are 24cm, or 240mm
Stretched length becomes 240.6mm
An increase of about 0.25% (maybe 0.5% for the side mains)
Small enough to be ignored (in my opinion. 0.5% of 20lb = 0.1lb )

So any increase in mains tension as a result of stringing the crosses may be mostly due to the frame changing shape during stringing.

at first when i read this, it kinda made sense, but come to think of it, if you were to pull a rope with 200lb of strength in opposite directions as opposed to pulling the two ends with only 100lb of strength in opposite directions, the rope isn't going to stretch a whole lot more, because it is not very stretchy

just my analogy.. dunno if it can apply to badminton strings

**Neil Nicholls** · 03-31-2005, 01:32 AM

Originally Posted by SWC_Ant

just my analogy.. dunno if it can apply to badminton strings

exactly.
if your rope is elastic, it will stretch.

**ants** · 03-31-2005, 01:39 AM

It all actually depends.. guess what.. 2 days ago i tried tensioning the other way round Main 28 Cross 26lbs.

**SWC_Ant** · 03-31-2005, 01:41 AM

Originally Posted by Neil Nicholls

exactly.
if your rope is elastic, it will stretch.

what i meant was i dont think badminton strings are THAT elastic, far enough that tension increase will be directly proportional to length increase, if you know what i mean... so even if the string is stretched for less than 1mm, 1lb of tension increase isn't impossible

(im not saying that <1mm is going to give 1lb of extra tension, just saying its not impossible)

**Neil Nicholls** · 03-31-2005, 02:00 AM

Originally Posted by SWC_Ant

far enough that tension increase will be directly proportional to length increase

isn't that what elastic means?

real example with BG66

I took a length of BG66 and hung 24lb of weight on it and measured the increase in length.
2570mm stretched to 2795mm

so a 240mm centre main would stretch to 261mm under 24lb tension
so how much extra tension do you think you'll get by stretching it another 0.6mm?

<edit>
umm, 0.5lb+
bit less than 0.6mm using BG66 though.
different strings would react differently though.
The stiffer the string, the bigger the difference.
So I would expect a smaller tension change with BG65 than BG66 because it is more stretchy

**SWC_Ant** · 03-31-2005, 02:10 AM

Originally Posted by Neil Nicholls

isn't that what elastic means?

real example with BG66

I took a length of BG66 and hung 24lb of weight on it and measured the increase in length.
2570mm stretched to 2795mm

so a 240mm centre main would stretch to 261mm under 24lb tension
so how much extra tension do you think you'll get by stretching it another 0.6mm?

oh.. i didn't know string stetches that much under tension

(im no stringer

) but thanks for all the measuring

2570mm (0lb) => 2795mm (24lb), so 240mm (0lb) => 261mm (24lb), so each extra pound should increase the total length by 0.875mm, so 0.6mm would make the tension go up about 0.69 pound...

also, the BG 66 is probably one of the more stretchy strings, considering its only 0.66mm thick. if say BG 65 stretches less, then 0.6mm can easily equate to 1lb

edit: oh is BG 65 more stretchy?

then im not sure.. maybe you should measure the BG 65 lengths for us too.. that would be great thx

**Neil Nicholls** · 03-31-2005, 04:31 AM

BG66 0.81%/kg
BG70Pro 0.92%/kg
BG65 1.17%/kg
BG80 1.23%/kg
BG68Ti 1.33%/kg

the values are (change in length) / (original length) per Kilogram tension

the 66 and 70pro where done quite a while ago, and I don't have any more lying around.
The 65, 80 and 68Ti were done today

It would be nice if someone else would have a go and see if they get anything similar.

**SWC_Ant** · 03-31-2005, 04:42 AM

Originally Posted by Neil Nicholls

BG66 0.81%/kg
BG70Pro 0.92%/kg
BG65 1.17%/kg
BG80 1.23%/kg
BG68Ti 1.33%/kg

the values are (change in length) / (original length) per Kilogram tension

the 66 and 70pro where done quite a while ago, and I don't have any more lying around.
The 65, 80 and 68Ti were done today

It would be nice if someone else would have a go and see if they get anything similar.

wow thanks for measuring out all those strings!!
i think it would be helpful if an experiment were conducted here at BC regarding string tension loss over say.. 1 month's time. i'll post about it (possibly in a new thread) tomorrow if im not busy
meanwhile, anybody else able to try this measuring thing would be helpful

cheers